Synthesis, Structural Characterization, and Antimicrobial Activity

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Nov 27, 2012 - ISRN Inorganic Chemistry ... most fundamental breakthroughs in medicinal history [11]. ..... and Longman, London, UK, 3rd edition, 1975.
Hindawi Publishing Corporation ISRN Inorganic Chemistry Volume 2013, Article ID 760754, 7 pages http://dx.doi.org/10.1155/2013/760754

Research Article Synthesis, Structural Characterization, and Antimicrobial Activity Evaluation of New Binuclear Niobium(V) Tartrate Complexes with Biologically Important Drugs H. D. Revanasiddappa,1 B. Vijaya,2 L. Shivakumar,1 and K. Shiva Prasad1 1 2

Department of Chemistry, University of Mysore, Manasagangotri, Mysore 570006, India Department of Chemistry, University of BDT College of Engineering, Davanagere University, Davanagere 577004, India

Correspondence should be addressed to H. D. Revanasiddappa; [email protected] Received 31 October 2012; Accepted 27 November 2012 Academic Editors: A. Karadag, A. Lehtonen, and M. Pellei Copyright © 2013 H. D. Revanasiddappa et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. e new binuclear niobium(V) complexes of the type [[NbO(L)C4 H4 O6 ]2 C4 H4 O6 ] (where L = DMH, IMH, IPH, FPH, TMT) were prepared with biologically important drugs and characterized by using elemental analysis; IR, 1 H-NMR, and UV-Vis spectral studies, and thermogravimetric analysis. e molar conductance measurement of all the complexes in DMF solution corresponds to 1 : 1 electrolytic nature. All complexes were of the pure diamagnetic character and were found to have six-coordinate octahedral geometry. e antimicrobial activity of these complexes has been screened against two Gram-positive and two Gram-negative bacteria. Antifungal activity against two different fungi has been evaluated and compared with controls. All the complexes inhibit the growth of both Gram-positive and Gram-negative bacteria to a competent level.

1. Introduction Metal ions play a vital role in a vast number of biological processes. Niobium ions form complex species with virtually all types of neutral and anionic donors. Niobium and its compounds have a broad spectrum of applications. ey are used for the fabrication of special materials for microelectronics and optics, superconductors, refractory materials, catalysts, and alloys [1–5]. As an important alloy element in steels, niobium can greatly affect the properties of a sample, such as the intensity at high temperature, the ability of tarnish resistance, and temper brittleness [6, 7]. Niobium steels are valuable constructive materials for the chemical and nuclear industries, jet and rocket engines, gas pipelines, and turbines [8]. e chemistry of the early transition metal peroxo complexes has received special attention due to their importance in a variety of biological, pharmaceutical, and industrial processes [9]. Uses of metal ions in therapeutic agents are known to accelerate drug action, and their efficacy is enhanced upon the coordination with a metal ion [10]. e antimicrobial properties of metal complexes have been recognized for centuries and have represented some of the

most fundamental breakthroughs in medicinal history [11]. However, Nb(V) complexes have been limitedly studied as the biocidal agents [12, 13]. us, we intended to study the ability of niobium complexes as good antimicrobial agents. e present work describes the preparation of new niobium(V) tartrate complexes containing active pharmaceutical drugs (Figure 1). e isolated complexes were studied via elemental analysis; IR, 1 H-NMR, and UV spectroscopies; and TGA. In view of the biological activity of the complexes and diverse coordinating ability of the ligands, we were provoked to study the niobium(V) complexes of nitrogenbased ligands against microbial strains, namely, E. coli, S. aureus, P. aeruginosa, and B. subtilis, and fungal strains A. �avus and A. niger were undertaken to study their role as microbial compounds.

2. Experimental 2.1. Materials. e ligands IPH (isothipendyl hydrochloride, SKF Ltd., India), IMH (imipramine hydrochloride, Sun Pharmaceuticals Ltd., India), DMH (desipramine hydrochloride,

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ISRN Inorganic Chemistry OH N N

N

N N

N S Trimeprazine tartrate (TMT)

N

N

S

S Isothipendyl hydrochloride (IPH)

N

N

Fluphenazine dihydrochloride (FPH)

N

N Imipramine hydrochloride (IMH)

N H Desipramine hydrochloride (DMH)

F 1: Structure of the pharmaceutical drugs.

Smith Kline and Beecham Ltd., India), FPH (�uphenazine dihydrochloride, SKF Ltd., India), and TMT (trimeprazine tartrate, Intas Laboratories Ltd., India), were received from pharmaceutical industries as gi samples and used as received. Among the solvents employed, DMF and DMSO were of spectroscopic grade and remaining solvents were of AR grade. 2.2. Preparation of Niobium(V) Solution. Niobium(V) solution was prepared [14] by fusion of 0.05 g of niobium pentoxide with 2 g of potassium pyrosulphate in a silica crucible and leaching the mass with 20 mL of 10% tartaric acid solution. e solution was then diluted to 100 mL using water, and this solution was used for the preparation of complexes. Fresh solutions were prepared whenever required. 2.3. Physical Measurements. FTIR spectra for samples were recorded using Jasco FT-IR-4100 spectrometer. 1 H-NMR spectra were recorded in DMSO-d6 on AMX-400 FT-NMR spectrometer. Electronic spectra of the complexes in the UVVisible region (200–900 nm) were measured using a Jasco UVIDEC-610 double-beam spectrophotometer with quartz cells. Electrical conductance measurements of the prepared complexes were done using an Elico CM-180 conductometer. Melting points were determined in an open capillary tube on Mel-temp apparatus. Magnetic susceptibility data in the room temperature were obtained from Gouy method using Hg[Co(SCN)4 ] as a calibrant. e TG and DTA patterns of the complexes were recorded on a Perkin Elmer US TGA-7 analyzer in the atmosphere of air. e carbon, hydrogen, and nitrogen contents of the complexes were determined by CHNS analyzer. Tartrate was determined volumetrically by using chloramines-T. Niobium was estimated gravimetrically by direct ignition to Nb2 O5 [15]. 2.4. Antibacterial Activity. e in vitro biocidal activities of the ligands and their niobium(V) complexes were tested

against four bacteria namely, S. aureus, E. coli, P. aeraginosa and B. subtilius by disk diffusion method [16]. e pure cultures of these organisms were obtained from the Department of Biotechnology, Bapuji Institute of Engineering and Technology, Davangere. e organisms used in the compounds were subcultured into sterile nutrient broth. Aer incubating the same organisms at 37∘ C for 3 h, the growth thus obtained was used as inoculums for the tests. Nutrient agar (28 gL−1 ) and nutrient broth were sterilized in conical �ask of suitable capacity by autoclaving at 15 lb pressure for 30 min. e agar medium was melted on water bath and cooled to 45∘ C. To the 20–25 mL molten agar 0.5–0.7 mL of 3-h-old sub culture was added aseptically, mixed well by gentle shaking, and allowed to attain room temperature in Petri dishes. e sterilized �lter paper disks (Whatman 41) were loaded with known volume of the test compound of known strength using micropipette to get the disk of desired concentration. e disks are placed over the growth media seeded with microorganisms, le for diffusion, and incubated at 37 ± 2∘ C for 24 h. e experiment is carried out with four replicates for each concentration. e antibiotic chloramphenicol was also screened under similar conditions for comparison as a standard, and the solvent DMSO was also put to know the activity. 2.5. Antifungal Activity. Antifungal activity of the test compounds was determined against two fungi, A. �avus and A. niger, by Bateman poisoned food technique [17]. ese fungi were cultured for seven days on Czapek’s agar in sterilized petri dishes under 12/12 h light and darkness. e ligand and its metal complexes dissolved in DMSO were added to 10–15 mL of sterilized media to achieve different concentrations at 35 ± 2∘ C and allowed the media for solidi�cation. e test fungi were taken as 2 mm disks from 10-day-old pure colonies and placed in the petri plates containing Czapek’s agar nutritive medium. e experiments were carried out in four replicates per treatment, and incubation was carried

ISRN Inorganic Chemistry

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T 1: Physical analytical and molar conductance data of niobium(V) complexes. Complex (𝟏𝟏𝟏 [NbO(DM)C4 H4 O6 ]2 C4 H4 O6 (𝟐𝟐𝟐 [NbO(IM)C4 H4 O6 ]2 C4 H4 O6 (𝟑𝟑𝟑 [NbO(IP)C4 H4 O6 ]2 C4 H4 O6

(𝟒𝟒𝟒 [NbO(FP)C4 H4 O6 ]2 C4 H4 O6

(𝟓𝟓𝟓 [NbO(TM)C4 H4 O6 ]2 C4 H4 O6

C 47.32 (48.29) 48.78 (49.14) 42.22 (42.89) 43.48 (44.53) 45.18 (45.82)

Found (Calc.) % H N 4.64 4.52 (4.69) (4.69) 4.84 4.59 (4.91) (4.58) 4.04 6.72 (4.06) (6.82) 4.52 7.55 (4.56) (7.99) 4.42 4.33 (4.45) (4.45)

out at 22 ± 2∘ C under 12/12 light and darkness. e radical growth of the colony was recorded aer 96 h of incubation.

2.6. Synthesis of Complexes. An ethanolic solution of corresponding ligands (each 50 mL of 4 mmol) was added to an aqueous solution of 3 mmol of niobioum(V) slowly with constant stirring. e solid complexes were precipitated immediately. e solid complex was dried in vacuo over fused CaCl2 (yield: 55%–62%).

3. Result and Discussion

3.1. Physical Properties. All the newly prepared complexes are coloured, nonhygroscopic, and stable at room temperature for long periods. ey do not possess sharp melting points (>300∘ C). e complexes are insoluble in water and other common organic solvents such as ethanol, methanol, and acetone but are soluble in DMF and DMSO. Analytical data of the complexes are given in Table 1. e data corresponds to the formula [NbO(L)(C4 H4 O6 )]2 C4 H4 O6 . e molar conductance of all the complexes for 10−3 M solution in DMF at room temperature was found to be in the range of 77–84 Ohm−1 cm2 mol−1 (Table 1) showing thereby 1 : 1 electrolytic nature of the complexes. is is consistent with the stoichiometry assumed for the complexes on the basis of analytical data. e magnetic susceptibility measurements carried out at room temperature were found to be diamagnetic. Indeed all the niobium(V) complexes reported in the literature are diamagnetic [18]. 3.2. Electronic Spectra. e electronic spectra of the niobium complexes in DMF show no absorption peaks in the visible region. e free ligands show sharp band in the 35714–38461 cm−1 region, while their corresponding complexes exhibit sharp peaks in the 34722–37037 cm−1 region. is may be assigned to 𝜋𝜋 𝜋 𝜋𝜋∗ transition. A weak band in the 32051–32679 cm−1 region present in the spectra of the ligands is shied towards a higher-energy region (32462–3112 cm−1 ) in the spectra of their complexes attributable to 𝑛𝑛 𝑛𝑛𝑛∗ transitions. e results obtained



Λ Ohm−1 cm2 mol−1



83

S

5.03 (5.19) 4.33 (4.56) 5.05 (5.09)

81

78 77 84

in the electronic spectra of the complexes are presented in Table 2. 3.3. IR Spectra. e major infrared spectral frequencies of the ligands and the selected IR data of their niobium(V) complexes are enumerated in Table 3. In ligands, the group R3 NH+ interacts with Cl− giving rise to a broad band in the region 2700–2300 cm−1 [14]. In the IR spectra of the corresponding niobium(V) complexes, these bands are absent indicating that the tertiary nitrogen atom of the side chain is involved in coordination to the metal ion. It was pointed out that the heterocyclic nitrogen atom attached to the alkyl side chain gives rise to a characteristic broad band in the 2970–2830 cm−1 region. In the spectra of the corresponding complexes, these bands are either absent or shied to a higher frequency (Δ𝜈𝜈 𝜈 𝜈𝜈 𝜈𝜈𝜈 cm−1 ) indicating that the heterocyclic nitrogen atom is coordinated to the metal ion. In aromatic derivatives, 𝜈𝜈(CSC) generally appears as a sharp band around 750 cm−1 region [19]. In the studied niobium(V) complexes, it has been found that there is no change in 𝜈𝜈(CSC) supporting the noncoordination of heterocyclic sulphur atom. e bands occurring at around 1550 cm−1 and at 740 cm−1 in IPH are due to 𝜈𝜈(C=N) and 𝜈𝜈(C–S) vibrations [20, 21], respectively. e 𝜈𝜈(C=N) bands present at 1550 and 740 cm−1 remain at the same position in the spectra of the complexes suggesting the noninvolvement of the pyridine ring nitrogen and heterocyclic sulphur atom of the ligand in bonding with niobium(V) ion. e coordination of bidentate tartrate is con�rmed by the bands at 1710–1680 cm−1 𝜈𝜈(COO) and at 1410–1380 cm−1 𝜈𝜈(COO) [22]. Bands observed in the 495–475 cm−1 region in the spectra of the complexes correspond to the Nb–O–Nb. Presence of 𝜈𝜈(Nb–O) modes has been excluded because of the absence of peaks in the 560–540 cm−1 region. ese complexes also exhibit two bands at 625–610 and at 480–460 cm−1 due to antisymmetric vibrations of the Nb–O–Nb bridge bond, respectively. Bands observed at 3100–3000 cm−1 region in the spectra of phenothiazine ligands as well as their niobium(V) complexes

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ISRN Inorganic Chemistry T 2: Electronic spectral bands of niobium(V) complexes.

Ligand DMH IMH IPH FPH TMT

Ligands/complex DMH 1 IMH 2 IPH 3 FPH 4 TMT 5

Electronic spectral bands, cm−1 37594 32051 37735 32679 37313 32467 37037 32573 35714 32051

Electronic spectral bands, cm−1 38168 32679 38461 33112 34722 32894 35714 32671 36496 32462

Complex 1 2 3 4 5

T 3: Characteristic IR bands (cm−1 ) of the ligands and their niobium(V) complexes.

𝜈𝜈(N–CH3 ) 𝜈𝜈(NH–CH3 ) 2830 — 2655 — 2560 — 2585 — 2530 —

Assignment 𝜋𝜋 𝜋 𝜋𝜋∗ 𝑛𝑛 𝑛𝑛𝑛∗ 𝜋𝜋 𝜋 𝜋𝜋∗ 𝑛𝑛 𝑛𝑛𝑛∗ 𝜋𝜋 𝜋 𝜋𝜋∗ 𝑛𝑛 𝑛𝑛𝑛∗ 𝜋𝜋 𝜋 𝜋𝜋∗ 𝑛𝑛 𝑛𝑛𝑛∗ 𝜋𝜋 𝜋 𝜋𝜋∗ 𝑛𝑛 𝑛𝑛𝑛∗

𝜈𝜈(N–CH2 ) Hetero 2915

𝜈𝜈as (OCO) —

𝜈𝜈s (OCO) —

𝜈𝜈as (Nb–O) —

𝜈𝜈s (Nb–O) —

𝜈𝜈(Nb–N) —

𝜈𝜈(C–S)

— 2923 — 2905 — 2895 — 2850 —

1710 — 1690 — 1705 — 1695 — 1705

1400 — 1390 — 1405 — 1395 — 1385

620 — 618 — 610 — 622 — 625

470 — 466 — 460 — 475 — 485

370 — 390 — 380 — 375 — 390

— — — 740 740 760 760 755 755



may be assigned to 𝜈𝜈(C–H) stretching of the aromatic ring system. e far IR spectra of studied niobium(V) complexes exhibit medium intense bands in the region 390–350 cm−1 assigned to 𝜈𝜈(Nb–N) modes [23�. is con�rms the participation of the nitrogen atom in coordination.

3.4. 1 H-NMR Studies. e 1 H-NMRspectra of the ligand IPH and its complex are presented in Figure 2. e ligands IPH and TMT exhibit a doublet at around 𝛿𝛿 1.3 ppm, which is assigned to –CH–CH3 , whereas the IMH, IPH, and TMT exhibit a sharp signal (singlet) at around 𝛿𝛿 2.68 ppm due to tertiary nitrogen attached to alkyl group, that is, –N–CH3 . e multiplet centered at 𝛿𝛿 3.58–3.52 ppm is attributed to –N–CH2 in all the ligands. e other multiplet at 𝛿𝛿 6.78–7.82 ppm in ligands is due to aromatic protons. e DMH showed a signal at 𝛿𝛿 9.76 ppm that is assignable to –NH proton. e Nb(V) complexes exhibit signals at around 𝛿𝛿 2.8 and 𝛿𝛿 3.64 ppm that indicate the shi of alkyl protons attached to tertiary nitrogen, thereby suggesting the involvement of tertiary nitrogen in coordination with Nb(V) ion. us 1 H NMR supports the conclusion drawn on the basis of IR data regarding the involvement of tertiary nitrogen atoms in bonding with Nb(V) ion. In the 1 H NMR spectra of

9

8

7

6

5 4 (ppm)

3

2

1

0

3

2

1

(a)

11

10

9

8

7

6

5

4

(ppm) (b)

F 2: 1 H-NMR spectra of (a) ligand IPH and (b) complex 3.

ISRN Inorganic Chemistry

3.5. ermogravimetric Study. e decomposition temperature of the complexes obtained from their thermograms and the data are presented in Table 4, and the thermograms of complexes 1 and 4 are depicted in Figure 3. ermogravimetric study indicates that all the complexes are thermally stable up to 220∘ C and the decomposition of the complexes takes place in two steps, namely, decomposition of organic moiety and the loss of tartrate followed by the formation of Nb2 O5 in the temperature ranges 220–330 and 330–555∘ C, respectively. e decomposition was slow in the beginning but rapid in later. e complexes attained constant weight between 600 and 700∘ C. e weight observed in each case was in full agreement with the weight loss calculated on the basis of the stoichiometry proposed for the complexes. From the previous spectral and thermal data, an octahedral structure for niobium(V) complexes was predicted in Figure 4. 3.6. Evaluation of Antimicrobial Activity. e ligands DMH, IMH, IPH, FPH, and TMT and their niobium(V) complexes were screened separately for both antibacterial and antifungal activities. e average percentage inhibition of both bacterial and fungicidal growth media compared to the respective controls was calculated by using the Vincent equation [24]. e screening data of average percentage inhibition of bacteria and the fungi at 30 𝜇𝜇g and at 60 𝜇𝜇g concentrations are given in Tables 5 and 6. e results clearly indicate that the complexes have both antibacterial and antifungal activities against the tested organisms. e results of the inhibitory activity of the synthesized complexes on the organisms show that in lower concentration the complex did not affect much on the bacterial and fungal growth. It shows that as the concentration of the complex increases, the inhibition of bacterial and fungal growth also increases. e screening of data reveals that the niobium(V) complexes show greater antimicrobial activity compared to the free ligands. A possible explanation for the toxicity may be explained by chelation theory [25]. It was suggested that chelation reduces the polarity of the metal ion considerably mainly because its positive charge is partially shared with donor atoms and 𝜋𝜋-electron delocalization over the whole chelating ring that is feasible. is increases the lipophilic character of the metal chelates, which favours its permeation through lipoid layers of the organism membranes.

4. Conclusions e molar conductance data indicate the 1 : 1 electrolytic nature of the newly prepared niobium(V) complexes. TG

T 4: ermogravimetric data for niobium(V) complexes. Weight loss (%) Found Calc.

Complex Temp.∘ range ( C)

Probable product

1

235–330 360–540

79.55 19.32

81.89 22.35

[(DM)2 (C4 H4 O6 )3 ] Nb2 O5

2

255–315 340–515

79.78 19.03

82.18 21.78

[(IM)2 (C4 H4 O6 )3 ] Nb2 O5

3

250–325 345–520

80.23 18.82

82.32 21.59

[(IP)2 (C4 H4 O6 )3 ] Nb2 O5

4

255–320 330–550

82.88 16.75

84.48 18.97

[(FP)2 (C4 H4 O6 )3 ] Nb2 O5

5

250–320 345–525

80.18 18.29

82.67 21.14

[(TM)2 (C4 H4 O6 )3 ] Nb2 O5

100 Weight (%)

niobium complexes, no change occurs at 𝛿𝛿 1.31 ppm and at 𝛿𝛿 6.78–7.8 ppm assigned to alkyl and aromatic protons, respectively. In complex 1 the signals at around 𝛿𝛿 2.85 and at 𝛿𝛿 3.33 ppm indicate a down�eld shi� of alkyl protons attached to the secondary nitrogen and heterocyclic nitrogen, thereby suggesting the involvement of secondary nitrogen as well as heterocyclic nitrogen atoms in coordination with niobium ion.

5

80 60 40 20 0 50

200

350

500

650

Temperature ( ∘ C) 1 4

F 3: TGA curve of complexes 1 and 4.

L

O

N N

L = DM O

O Nb

Nb O Tr

Tr

N

O O

N

IM Tr

TM IP

L

FP Tr = tartrate

F 4: Suggested structure of the prepared complexes (1–5).

studies suggest that all complexes decompose in two steps, and �nally they form their respective metal oxides. �ased on chemical composition and physico-chemical studies, a sixcoordinated dioxobridged binuclear structure has been proposed tentatively for niobium(V) complexes. e antimicrobial activity screened for the studied complexes against tested bacteria and fungi shows that niobium complexes display greater microbial toxicity compared to the free ligands.

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ISRN Inorganic Chemistry T 5: Antibacterial screening data of the ligands and their metal complexes. Percentage inhibition zone (±)a E. coli P. aregainosa 30 𝜇𝜇g 60 𝜇𝜇g 30 𝜇𝜇g 60 𝜇𝜇g 0.0 7.4 0.0 6.0 2.6 11.5 8.2 14.7 2.2 9.2 2.4 7.4 0.0 7.4 0.0 5.9 0.0 8.3 0.0 7.5 6.7 22.4 8.9 22.8 3.5 16.8 7.5 23.3 10.5 36.2 7.0 27.3 4.5 18.2 4.7 16.4 4.5 16.0 4.4 15.0 100 100 100 100

S. aureus

Compound 30 𝜇𝜇g 0.0 4.4 2.7 0.0 0.0 8.2 7.6 9.2 6.3 5.3 100

DMH IMH IPH FPH TMT 1 2 3 4 5 Chloramphenicol

60 𝜇𝜇g 8.5 9.7 8.7 6.2 5.4 19.0 17.4 33.2 13.1 11.2 100

B. subtilius 30 𝜇𝜇g 60 𝜇𝜇g 0.0 10.2 2.8 9.2 1.2 9.3 0.0 16.0 0.0 14.2 6.8 21.6 6.7 20.3 8.9 26.4 5.3 20.6 5.5 16.5 100 100

DMSO showed no inhibition, a each value is the average of four replicates.

T 6: Antifungal screening data of the ligands and their metal complexes. Percentage inhibition zone (±)a A. �avus

Compound DMH IMH IPH FPH TMT 1 2 3 4 5 Griseofulvin

30 𝜇𝜇g 0.0 3.6 13.4 0.0 2.0 8.2 7.3 13.5 4.2 3.5 100

60 𝜇𝜇g 5.2 3.2 28.4 5.4 10.2 23.3 27.3 38.4 11.7 17.3 100

A. niger 30 𝜇𝜇g 0.0 5.6 10.2 0.0 2.0 9.6 6.2 14.8 5.3 4.7 100

60 𝜇𝜇g 8.6 12.5 27.5 8.3 17.6 27.2 30.7 34.6 13.9 16.5 100

DMSO showed no inhibition, a each value is the average of four replicates.

Acknowledgment e authors are thankful to the University of Mysore, Mysore, India for providing �nancial assistance through a minor research project.

References [1] M. T. Tanvir, Y. Aoki, and H. Habazaki, “Improved electrical properties of silicon-incorporated anodic niobium oxide formed on porous Nb-Si substrate,” Applied Surface Science, vol. 255, no. 20, pp. 8383–8389, 2009. [2] H. Smogor, T. Cardinal, V. Jubera et al., “Effect of silver on phase separation and crystallization of niobium oxide containing glasses,” Journal of Solid State Chemistry, vol. 182, no. 6, pp. 1351–1358, 2009.

[3] A. M. R. Galletti and G. Pampaloni, “Niobium complexes as catalytic precursors for the polymerization of ole�ns,” Coordination Chemistry Reviews, vol. 254, no. 5-6, pp. 525–536, 2010. [4] A. Godeke, A. den Ouden, A. Nijhuis, and H. H. J. ten Kate, “State of the art powder-in-tube niobium-tin superconductors,” Cryogenics, vol. 48, no. 7-8, pp. 308–316, 2008. [5] M. E. Campderrós and J. Marchese, “Transport of niobium(V) through a TBP-Alamine 336 supported liquid membrane from chloride solutions,” Hydrometallurgy, vol. 61, no. 2, pp. 89–95, 2001. [6] L. Dongling, H. Xiaoyan, and W. Haizhou, “Separation and simultaneous determination of niobium and tantalum in steel by reversed-phase high-performance liquid chromatography using 2-(2-pyridylazo)-5-diethylamino phenol as a pre-column derivatizing reagent,” Talanta, vol. 63, no. 2, pp. 233–237, 2004. [7] H. Naja�, J. Rassizadehghani, and S. Asgari, “As-cast mechanical properties of vanadium/niobium microalloyed steels,” Materials Science and Engineering A, vol. 486, no. 1-2, pp. 1–7, 2008. [8] M. Sankar, Y. S. Reddy, and R. G. Baligidad, “Effect of different thermomechanical processing on structure and mechanical properties of electron beam melted niobium,” Transactions of the Indian Institute of Metals, vol. 62, no. 2, pp. 135–139, 2009. [9] H. omadaki, A. Lymberopoulou-Karaliota, A. Maniatakou, and A. Scorilas, “Synthesis, spectroscopic study and anticancer activity of a water-soluble Nb(V) peroxo complex,” Journal of Inorganic Biochemistry, vol. 105, pp. 155–163, 2011. [10] E. Melendez, “Metallocenes as target speci�c drugs for cancer treatment,” Inorganica Chimica Acta, vol. 393, pp. 36–52, 2012. [11] A. M. Elsome, J. M. T. Hamilton-Miller, W. Brum�tt, and W. C. Noble, “In-vitro and in-vivo antibacterial activity of plaunotol, a cytoprotective antiulcer agent, against Helicobacter pylori,” Journal of Antimicrobial Chemotherapy, vol. 37, no. 5, pp. 919–929, 1996. [12] Y. Shi, I. Harvey, D. Campopiano, and P. J. Sadler, “Niobium uptake and release by bacterial ferric ion binding protein,” Bioinorganic Chemistry and Applications, no. 14, pp. 1–11, 20102010. [13] B. Keshavan and H. Kempe Gowda, “Synthesis, spectral andfungicidal studies on dioxobridged binuclear niobium(V) and tantalum(V) complexes of N-alkylphenothiazines,” Turkish Journal of Chemistry, vol. 26, no. 2, pp. 237–243, 2002.

ISRN Inorganic Chemistry [14] A. R. Katritzky and A. J. Boulton, Advances in Heterocyclic Chemistry, vol. 9, Academic Press, New York, NY, USA, 1968. [15] A. I. Vogel, A Text Book of Quantitative Inorganic Analysis, ELBS and Longman, London, UK, 3rd edition, 1975. [16] A. L. Barry, “Procedure for testing antimicrobial agents in agar media. eoretical consideration,” in Antibiotics in Laboratory Medicine, V. Lorian, Ed., p. 1, Williams and Wilkins, London, UK, 2nd edition, 1980. [17] J. Bateman, R. D. Chapman, and D. Simpson, “Possible toxicity of herbal remedies,” Scottish Medical Journal, vol. 43, no. 1, pp. 7–15, 1998. [18] F. A. Cotton, M. P. Diebold, and W. J. Roth, “Binuclear alkoxide complexes of niobium and tantalum in lower oxidation states,” Inorganic Chemistry, vol. 24, no. 22, pp. 3509–3510, 1985. [19] A. P. Mishra, A. Tiwari, S. K. Gupta, and R. Jain, “synthesis, spectral and antimicrobial studies of some Co(II), Ni(II) and Cu(II) complexes containing 2-thiophenecarboxaldehyde moiety,” E-Journal of Chemistry, vol. 9, no. 3, pp. 1113–1121, 2012. [20] R. M. Issa, A. M. Khedr, and H. Rizk, “1 H NMR, IR and UV/VIS spectroscopic studies of some schiff bases derived From 2aminobenzothiazole and 2-amino-3-hydroxypyridine,” Journal of the Chinese Chemical Society, vol. 55, no. 4, pp. 875–884, 2008. [21] M. Senthilkumar and C. Ramachandraraja Growth, “Structural, spectral and optical studies on pure and L-alanine mixed bisthiourea cadmium bromide (LABTCB) crystals,” Journal of Minerals & Materials Characterization & Engineering, vol. 11, no. 6, pp. 631–639, 2012. [22] M. M. Alam, S. M. M. Rahman, M. M. Rahman, and S. M. S. Islam, “Simultaneous preparation of facial and meridional isomer of cobalt-amino acid complexes and their characterization,” Journal of Scienti�c �esearch, vol. 2, no. 1, pp. 91–98, 2010. [23] E. N. Nfor, S. N. Esemu, G. A. Ayimele, E. A. Eno, G. E. Iniama, and O. E. Offiong, “Synthesis, stereochemistry and antimicrobial activity of copper(II) and nickel(II) complexes of 4-phenylsemicarbazones,” Bulletin Chemical Society of Ethiopia, vol. 25, no. 3, pp. 361–370, 2011. [24] J. H. Kim, K. L. Chan, N. Mahoney, and B. C. Campbell, “Antifungal activity of redox-active benzaldehydes that target cellular antioxidation,” Annals of Clinical Microbiology and Antimicrobials, vol. 10, pp. 23–39, 2011. [25] M. A. Neelakantan, M. Esakkiammal, S. S. Mariappan, J. Dharmaraja, and T. Jeyakumar, “Synthesis, characterization and biocidal activities of some schiff base metal complexes,” Indian Journal of Pharmaceutical Sciences, vol. 72, no. 2, pp. 216–222, 2010.

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